body {
    /*取消浏览器内间距  外间距*/
    margin: 0;
    padding: 0;
}

.sub-nav {
    width: 100%;
    height: 80px;
    background-color: #FF8a00;
}

.sub-left {
    width: 300px;
    height: 100%;
    background-color: lightgray;
    float: left;
}

.sub-middle {
    width: 400px;
    height: 100%;
    background-color: gray;
    float: left;
}

.sub-right {
    width: 500px;
    height: 100%;
    background-color: #464646;
    float: right;
}
